This invention is directed generally to systems which monitor and record motion events. More particularly, it relates to the accurate management and control of time-sequential imaging and display, with application in numerous fields of science and technology. Most particularly, the invention provides a total race-management system which has wide ranging utility in measuring timed sporting events.
The invention also relates to systems and methods for generating a scene by compilating successively-scanned line objects. As such, the invention also concerns apparatus for compressing those scenes into manageable data files and for color coding scene information efficiently.
Prior art systems which track and record a motion event over time are overwhelmingly directed towards the support of racing events. Standard photographic techniques which monitor the finish line of a race are known. Typically, cameras equipped for high resolution imaging view the finish line and sequentially capture pictures at a high rate for later use by an interpreter. However, this process is cumbersome, wasteful, and time-consuming, requiring, for example, an apparatus of photographic film and paper, processing chemicals, and image enlargers or projection optics. Consequently, most races rely on human judges and revert to xe2x80x9cphoto-finishxe2x80x9d technology only in extremely close races. Specialty Instrument Corporation provides a myriad of such electronic and photo-finish systems under the trademark Accutrack(trademark). U.S. Pat. No. 3,829,869 exemplifies one such Accutrack(trademark) system.
Because of the problems with the xe2x80x9cphoto-finishxe2x80x9d technology, numerous other systems for monitoring racing events have been developed. However, these other methods and systems for timing sporting events present new difficulties. Video systems which record and display races in a standard television or video format are popular, but regardless of the particular implementation of these systems, a portion of the electronic image remains on an analog medium, e.g., video tape. Since analog data from the systems consists of a continuum of information over time, it is relatively difficult to accurately apportion to a unique time interval. It is even more difficult to access a particular moment in time in the recorded sequence because the associated system must search the storage medium, typically having a long physical length in a spooled format, e.g., a video cassette. This presents both limitations and difficulties for users wishing to simultaneously record, view the current race, and review earlier segments of the race (or even a previous race) because only one user can have access to any of the information stored and recorded at any one time.
A further difficulty in analog data is that it must be converted to a signal usable for video, television, or a computer before it is displayed. For example, after a completed search, the selected video tape segment is typically sent to active memory before it can be processed by a computer and, quite possibly, by supplemental complex graphics generators. Altogether, the analog format and related processing adds to the time required to review a race and therefore lengthens the decision making process.
Another problem faced by race systems occurs in the management of extended time events, like a marathon or bicycle race, which can last for hours or until each entrant finishes. The runners or cyclists cross the finish line in groups; and for long periods, the finish line is void of persons. The relevant information at the finish line is thus sporadic, and includes significant amounts of xe2x80x9cdeadxe2x80x9d time. In analog systems, this dead time is nevertheless recorded and stored so that the system can retain time synchronism with the event, even though it is generally useless for other reasons and adds to the time required for processing and reviewing the race.
Several race systems have attempted to improve the management and accessibility of data taken during a race by transforming the recorded information to a digital equivalent. But, these systems also revert to an analog format before displaying the race on a screen. As examples, U.S. Pat. No. 4,797,751 shows a video recording system having both digital and analog sections to provide display on a common cathode ray tube (CRT). U.S. Pat. No. 5,136,283 similarly describes another partially digital system which displays races on a standard television format. These analog/digital systems still have many of the problems inherent in all analog systems.
It is, accordingly, an object of the invention to provide a system for recording and displaying a time-sequential scene of bodies crossing a plane. In particular, the system provides improvements in managing and recording timed sporting events which reference bodies or entrants crossing a finish line relative to the start of an external event.
Still another object of the invention is to provide improvements in the manipulation of timed information representative of bodies passing a plane in space, such as person crossing a finish line in a race.
Yet another object is to provide improved access, control and storage of a scene comprising a sequence of discrete time images.
Most particularly, it is an object of the invention to provide a race monitoring and recording system which can record and display a race in a digital format.
Still another object of the invention is to store and display color scenes on a computer system with efficient color coding.
These and other objects will become apparent in the description below.
The invention features, in one aspect, a system for recording and displaying a time sequential scene of bodies moving across a plane in space. The system includes at least one digital camera which views and images a line object in the plane of interest. The camera time-sequentially captures the line object by imaging it onto an array of detector elements and converts the sampled signal into a digital image, or frame, of the line object. Each digital image frame uniquely represents a slice of the moving scene at a moment in time. The system also includes an image timer, with a timer processor, that responds to a preselected digital value from the camera and marks each frame with a digital time reference using a preselected number of bytes within the frame information. The image timer may also store the digital frames from the camera in an internal buffer. The system further includes a main control computer having an internal memory, a user console, and a graphics display monitor. The computer stores the frames from the image timer buffer as blocks of information in its internal memory, via an associated software pointer, and selectively displays a portion of the stored frames as a time-sequential scene on the monitor. A user at the computer console can command a variety of functions provided by the invention to manipulate and analyze the captured scene, most particularly to display any portion of the scene of bodies moving across the plane and access an associated time for any frame within.
The system thus summarized is particularly useful in recording and managing the official times of objects or entrants crossing a finish line, and at a rate which is over fifty times faster (and more accurate) than a related video race management system. A user can record and display the bodies crossing the plane of interest, i.e., the finish line, with accuracy while maintaining the ability to review and edit in real-time the stored images. Accordingly, it is useful that the time references associated with each frame are triggered with a start sensor and correlated to the start of an external event, e.g., a gun start signal. The invention thus provides, in another aspect, a timer clock that is synchronized to the start of an event and which provides the timer processor with an accurate reference to mark the respective moments in time for each frame.
In other aspects, the digital camera can include a line scan charge coupled device which forms the array of detector elements. The camera can also include a greyscale gain controller to adjust the digital output signal according to a preselected gain level, preferably selectable at the main control computer, and, preferably, to a gain level corresponding to the digital values in the captured frames. The gain controller can function in a real-time fashion by adjusting the greyscale gain applied to each frame as captured by the camera during operation of the invention. The camera is completely computer controlled from a remote location. This computer control, which is achieved by passing signals along the coaxial cable, allows remote control of focus, zoom, pan and all other camera functions.
In still other aspects, the resolution of the scene as captured by the camera, or as displayed on the screen, is selectable by a user. With respect to the camera, the resolution in the time-domain, i.e., in the direction of motion, is adjustable by selecting the frame rate at which the camera captures the digital image frames. The resolution in the spatial-domain, i.e., along the line object length, is adjustable by changing the camera density control which activates only particular detector elements in the array.
With respect to the resolution as displayed on the monitor, the user can, in another aspect, zoom a particular scene in or out on the screen. For example, by zooming the scene out, the whole race can be viewed at once; and by zooming in, particular areas of the scene are enlarged on the screen, suitable, for example, to interpret the number identifier of a particular runner. The zoom capability is available to users at the main control computer in either screen dimension, i.e., in the time and spatial directions, concurrently or independently.
A user of the system thus described has a variety of controls at the main control computer. Any frame of a displayed scene can be removed, either temporarily or permanently, according to other aspects of the invention by xe2x80x9ccroppingxe2x80x9d the frames. A list of xe2x80x9ccroppedxe2x80x9d frames is placed into a listing memory. A time-crop control allows a user to cut-out, or xe2x80x9ccropxe2x80x9d, uninteresting portions of the scenexe2x80x94for example periods of time containing no activity or bodies crossing the planexe2x80x94while retaining an absolute time reference for the remaining frames, which collectively display a continuous scene. The time-crop control further can restore the cropped frames, by deleting them from the listing memory, or permanently erasing them.
In another aspect, a user can also selectively reverse the time-sequential order of the displayed scene so that the scene as displayed appears as though the motion of bodies passing the plane in space occurred in the other direction. In addition, a user can point to particular bodies on the display to provide both an object identifier, if selected, and a unique time identification representative of the point selected.
The system constructed in accordance with the invention also provides, in another aspect, a virtual memory subsystem, like a hard-disc drive. The main control computer stores blocks of information into the virtual memory subsystem to free space in its own internal memory and to provide a storage medium for previous scenes, for example previous races. Storage into the virtual memory subsystem is initiated by an optional command or can occur automatically when a predetermined selectable fraction of the internal memory is utilized. The storage arrangement on the virtual memory subsystem is, in another aspect, ordered so that the main control computer can access and selectively retrieve a block of information from the virtual memory subsystem for storage in its internal memory by computing an offset from the initial memory location where the blocks of data are stored. In this manner, the internal memory of the main control computer can function as a cache for the virtual memory subsystem, thereby storing only a few active blocks in volatile RAM.
To aid the storage capability of the virtual memory subsystem, the invention accordingly provides a compression system to compress the blocks of information into less memory space. The compression system is selectively controlled, both in initiating the compression of certain data and in regulating the accuracy of the compressed information.
The compression system takes advantage of the fact that each digital image frame comprises a column of n-bit numbers, and a sequence of digital frames thus forms an array of rows of n-bit numbers. In a preferred aspect, the compression occurs by first converting the array of digital image frames to an array of rows of m-bit greyscale numbers (where the integer m is less than the integer n). The converted array of rows of m-bit digital image frames is then reformatted in a row-by-row fashion by collecting adjacent and equal m-bit numbers into a group and representing the collection as a xe2x80x9ccountxe2x80x9d and a greyscale xe2x80x9cvaluexe2x80x9d. These rows are reformatted again into a sequential memory string thereby compressing the data to a smaller amount. Preferably, the xe2x80x9ccountxe2x80x9d is either a byte or a 3-bit number, and the m-bit xe2x80x9cvaluexe2x80x9d is formed by a 5-bit representation of each of the original n-bit numbers, although the accuracy of the compression is selectable by a user by changing the number m. If the count is a 3-bit number, the count and value form one byte. For example, a 4-bit number can be used to compress the data further.
In yet another aspect, the invention can include a plurality of digital cameras, each with an associated buffer within the image timer, to independently capture a sequence of digital image frames. Thus multiple scenes are generated, preferably of a view containing substantially the same line object, for display on the computer. At least two scenes can be shown simultaneously on a single monitor from two separate cameras in both a real-time display or from previously recorded segments. In another aspect, one or more additional computers are installed in communication with the virtual memory subsystem to access and separately display and manipulate data captured by any one of the connected cameras. Thus, a second user can analyze previously recorded motion segments while a first user concentrates on a current motion event.
The digital camera and image timer each have associated processing CPUs which can selectively compress data before transmission along a signal line. For example, the digital camera can reduce the bandwidth requirements of the signal line or cabling between it and the image timer by commanding a first compression on the digital data transmitted from the camera. The image timer can reduce the bandwidth requirements of the cabling or signal line between it and the main control computer by commanding a second compression on the data transmitted between the two using a similar compression scheme.
In a preferred aspect, a single cabling is used between the image timer and camera. This cable preferably is in the form of a single coaxial cable that functions as a signal line to command various functions at the camera, a data transfer line to transmit digital information to the image timer, and a power line to supply power to the camera. Similarly, the cabling between the image timer and main control computer or any additional computers can have like capability.
In still another aspect, the main control computer allows a user to access an object identifier and an associated time corresponding to the object, e.g., for use in a race-management system. For example, prior to the start of a race, the lanes within the camera field of view can be spatially referenced to a portion of the displayed image such that when a user points to that portion, both the lane number and any associated object, e.g., a race entrant, is available on the display monitor. Further, according to an additional aspect, the time and name of a particular object is automatically entered within a results window on the display monitor once a user so commands it.
These and other aspects will become apparent in the following description, where the invention is described and illustrated in connection with certain preferred embodiments; however, it should be clear that various additions, subtractions, and modifications can be made by those skilled in the art without departing from the scope of the invention.